A number of continuous or semi-continuous conversion processes for base metal sulfide materials have been proposed. They can be broadly grouped into bath and flash conversion processes.
The former group includes continuous (or semi continuous) conversion of copper sulfide to semiblister copper and iron-containing base metal matter to crude metal or higher grade matter as discussed in U.S. Pat. Nos. 5,281,252; 5,215,571; and 5,180,423 (the Inco process); continuous copper conversion as discussed in Canadian patents 552,319 and 954,700 (the Mitsubishi process).
In the Inco process solid base metal sulfide materials are fed to the converter, while in the Mitsubishi process, the feed to the converter consists of molten matte. In both the Inco and Mitsubishi converters, the oxidizing gas is blown onto the molten bath by means of lances.
To the latter group belong the Into and Kennecott-Outokumpu flash conversion processes. In both these cases, finely comminuted high grade copper matte reacts with the oxidizing gas in suspension over the molten bath.
While all of the above processes represent major advances over traditional Peirce-Smith batch conversion, they have drawbacks. The operation of the Mitsubishi continuous converter depends on the supply of molten matte; thus, interruptions in primary smelting result in a net loss of production. Converter refractory erosion and corrosion by the very aggressive lime ferrite slag used in the process are also a problem, although this has been somewhat alleviated by intensive use of water-cooled copper blocks in the converter wall. Injection tuyere wear limits converter productivity in the Inco copper sulfide bath conversion process. In addition, the particular geometry of the system disclosed in U.S. Pat. No. 5,180,423 results in the generation of relatively high space velocities between the vessel end walls and the off-gas exit and, consequently, in high dusting when feeding finely comminuted materials by simple dropping onto the surface of the bath. Furthermore, this geometry limits the number of blowing lances to two and, in the conversion of iron-containing mattes, is not conductive to optimal delivery of the oxidizing gas to appropriate regions of the surface of the bath, thus resulting in occasional overoxidation of the slag (U.S. Pat. No. 5,215,571). Substantial dusting, in particular when processing high grade copper matte (white metal) is a problem inherent in flash conversion.
There are other bath continuous or semicontinuous smelting and converting processes such as the Noranda, El Teniente and Vanyukov processes, which use tuyeres to supply the oxidizing gas and even the solid feed to the smelting or converting vessel. Foaming of the slag may occur in these systems when the desired product, e.g. blister copper, results in the simultaneous production of highly oxidized slags. Also relevant are the Mitsubishi smelting furnace and the recently developed Isasmelt (also known as Ausmelt or Sirosmelt) processes which use lances to blow the oxidizing gas at high velocities to cause vigorous agitation of the bath. Refractory wear and rapid lance consumption are difficulties associated with these processes.
Assignee has pioneered the use of porous plugs in the converter to bottom sparge the bath from below the surface. Top blowing techniques have been developed to direct oxygen containing gases into the area directly above the porous plugs (U.S. Pat. Nos. 5,180,423 and 5,215,571). However, dusting is still a problem as noted in U.S. Pat. No. 5,281,252.